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NI USB-8473 Question About Configuring the Baud Rate

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Hi,

 

I am trying to set up a CAN bus monitor with the USB-8473 product.  

 

I can not see anything.  I have configured a microcontroller-based board as a node on the CAN bus.  I need to match the timing requirements for bot the uC and the NI USB-8473 board.  

 

I don't understand the difference between baud rate and bit rate.  

 

I have set my micrcontroller to the following bit rate settings: 

 

CAN Bus Bit Rate: 125 kbps

CAN Bus Clock : 40Mhz

BRP = 32    (BRPreg=31)

TSEG1 = 4

TSEG2 = 3

BT = 10

Triple Sample Mode

 

I program it to continually send a message on the CAN bus from Mailbox 0, with a certain ID, etc.  

 

 

In NI's MAX (Measurement and Automation Explorer) I set up a bus monitor as follows: 

In My System ->Devices and Interfaces -> NI-CAN Devices -> USB-8473 ->CAN0

 

In properties I choose "Edit the Segments of the Bit Timing Register" 

I select: 

BRP+1 = 6

SJW+1 = 1

TSEG+1=5

TSEG2+1=4

Triple Sample Mode

This results in a Sample Point of 60%

 

I have added a 150 ohm termination resistor on the CAN bus wire.  

 

All this results in 133.33 kBaud.

 

So, what am I doing wrong?  I can't see anything on the CAN Bus Monitor.  

 

What is the difference between kBaud and kbps.  

 

How do I set the timings of the two nodes the same?  

 

Thanks,

Rick 


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